The invention relates generally to electronic equipment cooling apparatus and in particular to a cooling fan for removal of operating heat from the interior of an electronic device.
It is a problem in the field of electronic equipment that generates heat during normal operation to remove the operational heat to prevent premature equipment failure. Various electronic components used in computers, such as microprocessors, generate heat during their normal operation. If not removed from the heat-generating component, the heat raises the device temperature to a level that degrades the reliability and service life of the device, and may also adversely affect nearby components as well. This problem has become more acute in recent years due to the increasing power and speed of microprocessors, and other electronic components, accompanied by correspondingly greater heat generation.
One heat dissipation solution has been to place one or more cooling fans in the computer housing and use the fan(s) to create a flow of cooling air through the housing. The fan receives at least a portion of the component operating heat and discharges it to ambient air surrounding the electronic equipment housing. The placement of one or more cooling fans in a electronic equipment housing, however, takes up valuable space within the electronic equipment which may already be at a premium for installation of other peripheral devices such as CD ROM drives, multiple floppy drives and larger hard drives.
In many types of electronic equipment, fans are used for cooling by way of blowing air over the electronics, thereby dissipating the excess heat generated by the electronics. Through proper sizing of the fan and flow control of the air driven by the fan, the electronic equipment can be maintained at a stable operating temperature even though ambient air temperatures may be quite high.
In many applications, however, the cooling fan represents one of the least reliable components used in an electronic system due to its primarily mechanical nature. In high availability electronic equipment, the cooling system must be further enhanced in order to increase its reliability. In one design technique, redundant fans are used in order to provide a backup cooling system when the primary cooling system fails. However, in order to maintain adequate airflow after the failure of a cooling fan, complete redundancy is required, thus increasing the cost, required space, and complexity of the electronic equipment.
An even more pressing design problem in highly compact computers, such as notebook computers, is that there may not be room for a separate cooling fan to remove operating heat. In this type of electronic equipment the designer must rely on radiation and natural convection from the exterior surface of the computer housing to remove the operating heat. This approach is limited by two factors. The maximum exterior surface area of the computer housing available for such radiant and convective operating heat dissipation, and the maximum temperature to which the exterior housing surface can be permitted to rise during computer operation before the housing becomes objectionably warm to the touch.
Computer peripheral equipment has used fans for many years to remove heat generated by electronic and mechanical sources. Recent advances in the size of transistors have elevated heat control to a primary limiting factor in many designs. When convection and conduction are insufficient to remove enough heat to maintain satisfactory operating temperatures, it is common practice to add a fan to the device for additional airflow. This adds cost, noise and increased physical size to the device at hand.
Typical computer peripherals such disk and tape drives employ one or more motors. It is possible to use these motors to move air in addition to their primary functions because the load presented by a fan blade is typically quite light in comparison to the other requirements of the motors.
A disk drive driven forced air cooling apparatus is disclosed by Nguyen (U. S. Pat. Nos. 5,793,740 and 6,359,856). In Nguyen, the spindle on which a data storage medium rotates also rotates a plurality of fan blades. The circumferentially sloped blades create a forced cooling air flow within the electronic equipment housing without requiring excessive additional space for a fan assembly or substantially increasing the cost. When the data storage drive rotates in one direction, the rotating blades create an axial flow of air that passes downwardly. Rotation of the data storage drive in the opposite direction create an axial flow of air that passes upwardly. The slope of the blade members dictates the direction in which the air flows.
A problem occurs when the apparatus is used in conjunction with a data storage device in which the disk drive motor rotation is bi-directional. Because reel motors in a tape drive must reverse direction periodically, it is not practical to couple them directly to a traditional fan blade for cooling purposes. This is because the heat generating sources (typically electronic circuit boards and the motors themselves) must be vented to the outside without routing hot air though the tape path itself which is sensitive to heat buildup. A venting design which moves hot air away from the tape path for one direction of motor rotation will move the hot air into the tape path when the rotational direction of the motor reverses. This can make the situation worse than no venting at all.
For these reasons, a need exists for a fan that will direct the flow of air in the same direction regardless of the rotational direction of the motor to which it is coupled.
The fan comprises a flat disk surface having a series of circumferentially spaced apertures wherein each aperture includes a V-shaped fan blade connected across the aperture perpendicular to the periphery of the disk-shaped surface. The V-shaped fan blade includes a pivoting device having a first blade member of one side and a second blade member of the opposing side of the pivoting device. In one position of the V-shaped fan blade, the first blade member covers a first portion of the aperture and the second blade members directs the flow of air downwardly through a second portion of the aperture. V-shaped fan blades allow the direction of the forced air to remain relatively constant when the rotational direction of the drive mechanism is reversed.
When the rotational direction of the drive mechanism is reversed, the flow of air pushes the second blade member downward causing the attached first blade member to pivot upward. When the first blade members is fully extended upward, the first portion of the aperture is uncovered and the first blade member directs the flow of air downwardly through the first aperture.